1. Field of the Invention
The present invention relates to friction coupling mechanisms such as brakes wherein a rotatable element is frictionally coupled to a relatively nonrotatable element and clutches wherein two relatively rotatable elements are coupled and uncoupled. More particularly, the invention relates to friction coupling mechanisms wherein a cam is used to achieve force multiplication in an air-actuated force intensifying piston and cylinder assembly.
2. Description of the Prior Art
Hydraulic and hydraulic-pneumatic brakes and clutches having friction members driven outwardly in opposite directions to engage opposed discs have been described in Suppes et al, U.S. Pat. Nos. 3,237,738 and 3,311,205 and 3,584,717, as well as in Montalvo, U.S. Pat. Nos. 3,696,900 and 4,175,651. The devices disclosed in those patents are compact and easy to service. The present invention incorporates advantageous features shown in the above identified patents, and more specifically, the present invention represents an improvement upon the piston and cylinder assembly disclosed and claimed in Montalvo U.S. Pat. No. 4,175,651, the disclosure of which is incorporated by reference herein in its entirety.
Force multiplication, as applied to brakes and clutches, is not a new concept. Bauman, U.S. Pat. No. 3,268,038 discloses a vehicular braking mechanism which utilizes differential area pistons in a wheel cylinder wherein applied braking force is intensified for actuation of the vehicle's brake shoes. Montalvo U.S. Pat. No. 4,175,651 discloses a friction coupling mechanism for use in brakes and clutches where force intensification is achieved by use of a compound piston arrangement, and Falk U.S. Pat. Nos. 4,089,393 and 4,154,321 disclose a disc brake system where force multiplication is achieved through use of a pair of cams mounted on a movable cam carrier.
The concept that when a force is directly applied to one of two opposed friction shoes or pads, there is a simultaneous application of an equal reaction force indirectly imposed on the other shoe, by reason of a self-aligning piston and cylinder assembly, is also not a novel concept, as the same has been suggested in Montalvo U.S. Pat. No. 4,175,651.
Despite the wide variety of prior art clutches and brakes, there continues to be a real need for improved friction coupling mechanisms that combine compactness with high torque capability, especially for industrial applications where space is limited.